The present invention relates to a method and apparatus for wire bonding which includes a position detecting operation as well as a method for producing a semiconductor device by using the wire bonding apparatus.
In an assembly of a semiconductor device, when a pellet, set on a tab of a lead frame, is electrically connected to a lead in the lead frame through a bonding wire by a bonding tool to connect the bonding wire to a bonding pad of the pellet or the lead frame, it is important to accurately grasp the landing or contact position of the bonding tool at the bonding pad or the lead frame and to exactly halt the downward motion of the tool so as to provide an adequate bonding load as well as to prevent a collision as a result of the bonding tool being moved downwardly to the bonding pad or lead frame against the pellet or lead frame with a significant mechanical impact or impulse.
For example, it is possible to provide for detecting a landing or contact of the bonding tool by sensing a positional displacement of a bonding arm to which the bonding tool is secured through a mechanical contact of the like in response to a tool landing or contact since such bonding arm is rotatably attached to a rotary shaft mounted on a vertical movable block.
However, a disadvantage of such proposed construction resides in the fact that in a wire bonding apparatus for a landing or contacting of the wire bonding tool is detected through a mechanical contact, the response speed to the landing is relatively slow and, through repeated use of the contact, it is unavoidable that the contact is worn to consequently bring about a change with the passage of time in the open position of the contact. Thus, it becomes impossible to attain an exact detection of the landing or contact position of the bonding tool. Moreover, it has also been found that a so-called chattering phenomenon occurs in that the vertical movement of the bonding tool is unstable. Furthermore, the operation or service time of the apparatus is reduced due to the necessity of maintenance service including repair and replacement of worn contacts.
Additionally, a further disadvantage of the proposed apparatus employing mechanical contact resides in the fact that the unstable and inaccurate upward and downward motion of the bonding tool causes incomplete joining of the bonding wire to the bonding pad of the pellet and also to the lead frame or damage and/or breakage of the pellet induced by the bonding tool thereby considerably reducing the reliability of the wire bonding and that of the semiconductor device.
A wire bonding arrangement of the aforementioned type is disclosed in, for example, "Electronic Materials", Industrial Research Inc., Supplement Volume, Nov. 10, 1981, pp. 158-162.